Safety switch for welding holders



c 13, 1953 A. T. TETRAULT 2,655,580

SAFETY SWITCH FOR WELDING HOLDERS Filed Dec. 14, 1951 F'Lgi' 1o IE/17.1l/l/I/l/III/l/A I I III :Lq

INVENTOR ANDREW T. TETRAULT 7197mm flwm v ATTORNEYS Patented Oct. 13,1953 UNITED STATES PATENT OFFICE SAFETY SWITCH FOR WELDINGHOLDERS AndrewT- il tr ult, In an Orchard, Mass.-

Application December 14, 1951, Serial No. 261,725

2 Claims.

This invention relates to a safety switch for a welding holder, and moreparticularly to a safety switch of the type stated that is adapted toprevent a circuit from being closed through the welding tool when thetool is not :in use.

Accidents tend to occur during the use ,of \a tool of type stated, inthat the worker may accidentally cause a circuit to be closed throughthe tool during welding operations at a time when it is essential thatthe circuit remain open.

The main object-of the invention, accordingly, is to provide a safetyswitch readily applicable to a tool used in electric welding, saidsafety switch being depressible by the worker when the tool is "held inits natural position during weld.- ing operations, the safety switchconstituting the present invention being so arranged as to moveautomatically to a circuit-opening position when the user releases hispressure thereupon.

Another important object is to provide a safety switch of the typestated which can be embodied in conventional welding tool constructionwithout the necessity of extensive modification or redesigning of thetool.

Another important object is to provide a safety switch as described soformed as tocause a good electrical contact to be made when the switchis depressed, thus to assure that the spaced concluctor bars bridged bythe contact will bear the electrical load equally.

Another important object is to provide a safety switch as describedwhich will be so located when in its inoperative position as to bedepressed to a circuit-closing position merely by the user grasping thetool naturally for the performance of the welding operation.

Yet another important object is to provide a safety switch which will beinexpensive to construct, and will comprise a minimum of simply arrangedpar-ts.

Other objects will appear from the following description, the claimsappended thereto, and from the annexed drawing, which like refer.- encecharacters designate like parts throughout the several views, andwherein:

Figure 1 is a top plan view of a welding tool equipped with a safetyswitch formed in accord ance with the present invention;

Figure 2 is a longitudinal sectional view taken substantially on line2-2 of Figure '1'; and

Figure 3 is an enlarged cross-sectional view taken substantially on line3.3 of Figure 2.

Referring to the drawings in detail, the reference numeral has beenapplied to the body of a welding tool, said "body being formed of an "2insulating material and being provided with a longitudinal bore 12-opening at opposite ends of the body. At one end of the body acounterbore 44 is provided, receiving a conductor it through whichelectrical current is supplied.

Embedded in the other end of the body are longitudinally contacting,flat plates is of electrically conductive material, said plates havingoutwardly oifset, intermediate portions and being fixedly connected byrivets 20 or equivalent fastening elements.

The outwardly offset intermediate portions of the plates rs define acavity between the plates [8, in'which is disposed a spring :22 exertingits pressure against a pivoted lever 24 to force said lever against awelding stick 26.

All this is conventional construction, and does not, sc constitute partof the present invention, these parts being illustrated and describedmerely to show their association with the which I have devised.

In accordance with present invention, an elongated bar 28 ofelectrically conductive material is embedded within the longitudinalbore l2 of the holder "body 10, said bar being connected atone end tothe conductor 16, so that an electrical current may be fed through thebar when the tool is being used. The other end of the bar 28 is beveled,as at 80.

A second electrically conductive bar 82 is formed to a circularcross-sectional configuration corresponding to that of the :bar 28, andis aligned coax-iall-y with the bar :28 within the bore I2 of the holderbody. The bar 32 at one end is in electrical contact with the flatplates It, and at its other end is beveled, as at 34, the bevel of thesecond bar being directed oppositely to the bevel .of the bar 28, as maybe readily noted from Figure *2.

The bevcled ends 30 and 34 of the conductive bars project slightly intothe lower end of a transverse passage 36 formed in the body andcommunicating with the bore I 2, said beveled ends being disposedslightly above the inner end '37 0'1 the passage, as maybe readily notedfrom Figure 2 or 3, thus to provide clearance for a depressible contactto be described hereina'fter, when the engaging surfiaees of "thecontact and of the conductive bars begin to wear after long usage. Theouter end of the passage open upon the outer surface of the holder bodyand communicates with a shallow recess 38 formed in said outer surfaceof the body.

A mounting plate-4U is seated in and is formed complementaril-y to therecess 38, and is secured 3 fixedly to the holder body by a plurality ofscrews 44 or equivalent fastening elements. In the present instance,four screw have been illustrated, but more or less can be employed, ifdesired.

It is believed sufllciently obvious as not to require specialillustration, that, if desired, the mounting plate 40 need not berecessed within the surface of the holder body, and can instead bemounted directly against, or even elevated above, said surface.

Formed in the mounting plate 40 is a center opening 42 formed to adiameter smaller than the diameter of the passage 36 and registeringwith said passage. A stem 46 of insulating material is slidable withinthe opening 42, the outer end of the stem projecting beyond the surfaceof the holder body, and the inner end of the stem extending into saidbody. Formed on the outer end of the stem 46 is an enlarged head 48, andabutting at one end against the head 48 is a spring 50 through which thestem extends. The other end of the spring 50 abuts against the mountingplate 40 and is fixedly secured to the mounting plate.

A small screw 52 is threaded into the stem 46 contiguous to the head 48,and the upper end of the spring 50 is looped about said screw and isfixedly connected to the stem through the medium of the screw. As aresult, the spring, being fixedly secured at its opposite ends to thestem and mounting plate, respectively, prevents rotatlon of the stemwithin the opening 42, while still permitting axial sliding movement ofthe stem.

Secured to the inner end of the stem 46 is an electrical contact 54 ofconductive material having oppositely beveled sides (Figure 2) that arecomplementary to the beveled ends 36 and 34 of the respective conductivebars. The contact 54 has a fiat upper surface abutting against the stem,and is secured fixedly to the stern by a screw 56, or its equivalent.

The upper surface of the contact 54 is of greater area than that of theopening 42, and as a result, when the spring 50 biases the stem 46upwardly, the contact 54 engage against the edge of the opening 42 tolimit movement of the stem outwardly of the body.

The bottom surface of the stem (Figure 3) is rounded so as to align withthe rounded bottom surfaces of the conductive bars 28 and 32 when theitem is depressed against the action of the spring 50.

By reason of the construction illustrated and described, it will bereadily appreciated that normally a circuit cannot be closed through theconductive bars 28 and 32 by reason of the fact that the spring 50 tendsto bias the stem 46 outwardly of the body, thereby causing the contact54 to move out of engagement with the respective conductive bars. Thedepression of the stem 46 against the action of the spring 50 isefiective to shift the contact into engagement with the oppositelybeveled ends of the conductive bars, causing a circuit to be closedthrough the bars to the welding stick 26.

The positioning of the bars 28 at an elevation slightly above the innerend of the passage 36 is effective to compensate for Wear of thecontacting surfaces of the bars 28 and 32 and of the contact 54. As thiswear occurs, the contact tends to move below the bars, and is permittedthis movement while still maintaining a good electrical contact with theconductive bars.

It is believed clear that the invention is not necessarily confined tothe specific use or uses thereof described above, since it may beutilized for any purpose to which it may be suited. Nor is the inventionto be necessarily limited to the specific construction illustrated anddescribed, since such construction is only intended to be illustrativeof the principles of operation and the means presently devised to carryout said principles, it being considered that the invention comprehendsany minor changes in construction that may be permitted within the scopeof the appended claims.

What is claimed is:

1. In a safety switch for an electric welding holder, the combinationwith a holder body having a longitudinal bore and a transverse passagecommunicating with and extending laterally from the bore, said passagehaving a closed inner end and having an outer end opening upon the outersurface of the body, and with a pair of electrically conductive barsarranged coaxially within said bore, said bars having spaced,confronting, oppositely beveled ends projecting into the passage andspaced from the inner end of the passage, of a stem of insulatingmaterial mounted within the passage to slide transversely of the bodytoward and away from said bars and having its opposite ends disposedwithin and without the body, respectively; a mounting plate fixed to theholder body and having an opening registering with said passage andformed to a diameter smaller than that of the passage; a springinterposed between and fixedly secured at its opposite ends to saidplate and to the outer end of the stem, respectively, and normallybiasing the stem outwardly of the body away from said bars; and anelectrically conductive contact on the inner end of the stem having itsopposite sides formed complementarily to the bevels of said ends of thebars and adapted to bridge said ends upon depression of the stem againstthe action of the spring for closing of an electrical circuit throughthe bars, the space between the inner end of the passage and said barends providing an open area into which said stem is shiftable on wearingof the bar ends, said contact being enlarged relative to the stem andengaging against the edge of the opening of the plate on biasing of thestem outwardly of the body to limit movement of the stern away from thebars.

2. In a safety switch for an electric welding holder, the combinationwith a holder body having a longitudinal bore and a transverse passagecommunicating with and extending laterally from the bore, said passagehaving a closed inner end and having an outer end opening upon the outersurface of the body, and with a pair of electrically conductive bars ofcircular cross-section arranged coaxially within said bore, said barshaving spaced, confronting, oppositely beveled ends projecting into thepassage and spaced from the inner end of the passage, of a stem ofinsulating material mounted within the passage to slide transversely ofthe body toward and away from said bars and having its opposite endsdisposed within and without the body. respectively; a mounting platefixed to the holder body and having an opening registering with saidpassage and formed to a diameter smaller than that of the passage; aspring interposed between and fixedly secured at its opposite ends tosaid plate and the outer end of the stem, respectively, and normallybiasing the stem outwardly of the body away from said bars; and anelectrically conductive contact on the inner end of the stem having aflat upper surface and a curved bottom surface aligning with the bottomsurfaces of the bars on movement of the stem inwardly of the body towardthe bars, said 10 Number 6 being of greater diameter than the diameterof said opening of the mounting plate and engaging against the edge ofsaid opening on biasing of the stem outwardly of the body to limitmovement of the stem away from the bars.

ANDREW T. TETRAULT.

References Cited in the file of this patent UNITED STATES PATENTS NameDate 1,340,270 Jahoda May 18, 1920 1,691,291 Kahaleohu Nov. 13, 19281,754,353 Endebak Apr. 15, 1930

